Ceramic Knives have their blades made from zirconium oxide. So far, diamonds are the only material that we know is harder.
To make the blades, ceramic powder with binders in it is put into moulds, then fired for several days, creating shaped knife blades which are then polished and ground. Then the handle is attached. Black bladed ones are more expensive than white ones.
Ceramic Knives aren’t made as long as knives with metal blades; the longest ceramic blades being made are 6 inches (15 cm.)
The blades can stay sharp for years without sharpening, and won’t rust or stain.
Still, Ceramic Knives will never be as sharp as a sharp metal knife, so they are not as good for paring, only slicing. But they are good knives for those who would never get around to getting steel knives sharpened, as they’ll have sharp knives longer. Some people, though, find them too light: they prefer a knife to have more “heft.”
Use Ceramic Knives for slicing, not chopping, or they will go dull on you. Use them only on cutting boards; they will damage the glaze on plates.
Most Ceramic Knives come with a list of instructions about what not to use them for. This can be problematic if you have lots of other people — friends, guests, etc – who aren’t aware of the more delicate treatment the knife requires.
Many people have one that is missing the tip from an accident. The blades can shatter if they are dropped, and the tips of the blade are particularly vulnerable, Don’t use the tip to pry anything open, as that can snap the tip off. Don’t put Ceramic Knives in the dishwasher — shaking in the dishwasher against other items could shatter the tip. Don’t drop them down into knife blocks, as the tip may hit bottom and shatter. Don’t use with frozen or bony foods, because the blades may chip.
When sharpening is needed, you must send them back to the manufacturer. Some manufacturers will for free re-sharpen the knives for you within a 3 or 5 year warranty period, though you do have to pay the postage to get it to them. Some gung-ho souls sharpen the knives themselves at home, but you need diamond stones to sharpen them against and a tool to hold them at the correct angle they require (an “obtuse bevel.”)